The present invention relates to a magnetic recording and reproducing apparatus and, more particularly, to such apparatus which includes signal processing circuitry mounted upon a rotary head drum.
Magnetic tape recording and reproducing apparatus, such as video cassette recorders (VCRs), used for processing video signals or other high density, large-volume digital data must handle recording and reproduced signals of high frequency. In such applications, an arrangement is known in which a recording/reproducing head is mounted on a rotary head drum and magnetic tape is transported across the drum while the drum is rotated, thereby enhancing the relative head-to-tape speed.
The transmission of recording and reproduced signals, as shown in FIG. 3, is generally implemented using a rotary transformer and achieved using a coil of a rotor in an upside (rotary) cylinder and a coil of a stator in downside fixed cylinder. Prior art VCRs for public use and broadcasting service require amplification by a pre-amplifier inside the rotary head drum, since the reproduced signals from the magnetic head are very weak. The pre-amplifier is mounted inside the rotary head drum to reduce noise between the magnetic head and the pre-amplifier and avoid a degradation of S/N (signal to noise) ratio caused by the transmission loss of the rotary transformer. The longer the distance between the magnetic head and the pre-amplifier, the more the stray capacitance between them increases. This adversely affects wideband signal transmission characteristics.
When a pre-amplifier is mounted inside the rotary head drum, as described above, operating power must be supplied to it. In the past, transmission of operating power to the reproducing preamplifier required the use of slip rings and brushes, as shown in FIGS. 1 and 2. Operating power and recording/reproducing changeover signals, etc. from the brushes were transmitted by the slip rings which rotate with the upside cylinder of the rotary head drum.
With this arrangement, however, imperfect contact between the slip rings and brushes occurred as they became worn and dirty, causing a voltage drop from the supply source. This in turn led to unstable operation of the reproducing pre-amplifer and resulted in the generation of noise. Hence, there was a need for the periodic maintenance and service of slip rings and brushes.
Recently, instead of slip rings and brushes, it has been proposed that operating power be transmitted by another rotary transformer (as shown in Japanese Tokkai Nos. 60-201502 and 61-42702). However, use of another rotary transformer for providing the operating power creates a space problem, particularly in the case of recording and reproduced high-definition signals and digital TV signals, since a plurality of rotary transformers are required for transmitting recording and reproduced signals.